Cephalosporins having an .alpha.-ureido acyl side chain and 3-position substituents other than heterothiomethyl are disclosed by Erickson in U.S. Pat. No. 3,673,183, by Welch et al. in U.S. Pat. No. 3,708,479, and by Dolfini et al. in U.S. Pat. No. 3,833,568. Cephalosporins having an .alpha.-ureido acyl side chain and a heterothiomethyl group in the 3-position are described as starting materials in the preparation of various acylthiomethyl esters by Breuer in U.S. Pat. No. 3,860,591, Cephalosporins having an .alpha.-ureido acyl side chain and a triazolylthiomethyl group and an oxopyridazinylthiomethyl group in the 3-position are disclosed by Breuer et al. in U.S. Pat. Nos. 3,996,217 and 3,996,218.
7.alpha.-METHOXY CEPHALOSPORINS HAVING AN .alpha.-UREIDO ACYL SIDE CHAIN AND A HETEROTHIOMETHYL GROUP IN THE 3-POSITION ARE DISCLOSED BY Dolfini in U.S. Pat. Nos. 3,978,051; 3,989,693; 3,989,697; and 4,000,134.
Cephalosporins having an .alpha.-acylureido acyl side chain and a heterothiomethyl group in the 3-position are disclosed by Cooper et al. in U.S. Pat. No. 3,925,368 and German Offenlegungsschrift No. 2,514,019, of Cooper in U.S. Pat. No. 3,956,292, and by Kocsis et al. in U.S. Pat. No. 3,954,802.
Cephalosporins having various heterothiomethyl groups in the 3-position and .alpha.-amino acyl side chains are disclosed as possessing antibacterial activity in U.S. Pat. Nos. 3,641,021; 3,759,904; 3,813,388; 3,821,207; 3,878,204; 3,796,801 (method of treating Enterobacter infections), etc. Also disclosed as useful intermediates are cephalosporins, substituted in the 3-position with --CH.sub.2 --S--hetero groups and in the 7-position with a ##STR3## U.S. Pat. No. 3,819,621.